kicad-developers team mailing list archive

[Vesa Solonen <vsolonen@xxxxxxxxx>]

On Mon, 30 Aug 2010, Alex G wrote:

> :-p ). The most I'm planning to tackle is 200A at 7V switched from the
> AC line.

Sounds interesting, especially the possible uses (please tell off the 
list ;) If 100Hz switcher counts, I've made such from (really)old 
telecom psu components about ten years ago. 70kgs with wheels, but _very_ 
difficult to break. Just some weeks ago I thought updating the controller 
design to the digital age and also replacing SCRs with synthetic mosfet 
ones to cut 300W from the losses. Fortunately I got my sanity back a few 
minutes later :)

> What do you use for generating the artwork? I need to stick two
> transparencies on top of each other to avoid pinholes. And if I'm lucky,
> I get horizontal lines of toner going straight through the board, just
> asking for a nice cutter-job after the board is etched.

I guess you are using a laser printer? Better UV-opacity is obtained with 
blue+yellow inkjet. I've seen some using it for 5mil work and that's 
amazing. They probably used better collimated light source than a led 
matrix though. I'm mostly doing toner transfers for prototypes with 12mil 
minimum width. Free laminate scrap helps...

The etch chemistry means a lot in home brew with inefficient agitation 
etc, and the finest + cheapest is stabilized sulphuric acid-hydrogen 
peroxide aka "peroxy-sulfuric" etch. Works very well unstirred, excellent 
etch quality (can be made even levelling or polishing) no fumes, just some 
very minor mist when etching is in progress due to peroxide decomposing. 
Stabilizers are usually phosphoric acid and phenol sulfonic acids at 
around 1g/l. Some aspirin dissolved in hot H2SO4 will do if phenol is 
unobtanium. Google will find a lot more details. Just remember to store 
all peroxide stuff in vented containers and remember that chlorides 
increase decomposition rate, so it may be wise not to use tap water for 
making the etch.

Before I forget to mention, the library discussion is very interesting :)
-Vesa